EP1858810B1 - Device and method for the electrolytic treatment of water and aqueous solutions - Google Patents

Description

The invention relates to a device for the electrolytic treatment of water or aqueous solutions with an inlet for the liquid to be treated and an outlet for the treated liquid and with an electrolysis device, which has arranged between the inlet and the outlet electrodes, which on mutually different electrical potentials can be placed, wherein the potential difference is chosen at least so large that an electrolysis of water and / or chloride ions contained in the water can take place, wherein the electrodes comprise at least one anode and a cathode, and wherein a first anode region, the an oxidation-stable material is manufactured, and another anode region, which is at least partially made of a carbon material, are provided.

Such a device is from the JP 2000 087275 known.

The DE 198 59 814 A1 also describes an electrolytic treatment of the water in an electrolytic cell. Here disinfectant species such as chlorine, hypochlorous acid or oxygen are produced anodically from water itself and natural water constituents such as chloride ions. The material used for the electrodes is titanium coated with noble metal mixed oxides. Such electrodes are chemically inert to the electrolytically produced disinfectants. A disadvantage of this is the high price of such electrodes, which therefore naturally have only a small surface area. Although they are therefore effective for disinfection, but not to prevent the formation of stones by electrolytic treatment of aqueous solutions.

The DE 100 30 340 C2 and EP 1 036 769 B1 describe devices for preventing scale formation by electrolytic treatment of aqueous solutions. Both devices comprise as anode a bed of carbon particles into which a power supply protrudes. Such anodes have proven excellent in devices for preventing unwanted lime precipitation by electrolytic treatment of water or aqueous solutions. They have a large surface and are easy and inexpensive to produce in any shape. However, such anodes can not be used for the electrolytic production of disinfecting species such as chlorine, hypochlorous acid or oxygen, because the disinfecting substances are adsorbed on the surface of the carbon particles, in particular on activated carbon particles, or chemically abreact with the carbon particles and thereby oxidizing them so that the measurable concentration of free disinfectant in the treated water is negligible.

From the the EP 0 175 123 B1 is a device and a method for the sterilization and simultaneous decalcification of liquids with an electrolytic cell, which is supplied via a control electronics with the necessary voltage known. Both electrodes of the electrolytic cell consist of the same, chlorine-resistant material. The germs contained in the liquid passing through the electrolytic cell are killed by electrolytic dissociation. At the same time, a reduction in hardness takes place in the catholyte space in the form of a cathode deposition in which calcium carbonate precipitates. In order to dissolve the calcium carbonate deposit at the cathode, a flux and polarity change at the electrolytic cell is necessary. For very hard water, this switching must be done very often. Such reversals are particularly disadvantageous, because on the one hand lime deposits can be removed only incompletely and on the other hand, the service life of the electrodes can be significantly shortened.

JP 2000 087275 describes an electrolytic cell for the production of carbonic acid. The electrolysis cell known from document 1 has an anode, which comprises a first anode region made of an oxidation-stable material and a further anode region made of carbon material. Both areas are simultaneously flowed through in parallel

Object of the present invention is in contrast to avoid the above-mentioned disadvantages and to provide a method and apparatus of the type mentioned, with which water is treated so electrolytically that on the one hand unwanted Kalkausfällungen be prevented in a more efficient manner, on the other hand, the water to be treated disinfected, and at the same time the life of the electrodes is extended over the prior art.

This object is achieved in a surprisingly simple, but effective manner in that the first and the further anode region are arranged electrically isolated from each other.

At the first anode region, which consists of an oxidation-stable material, the disinfectants are produced electrolytically. The anode material of the first anode region is here exposed not only to an acidic medium, but in particular also to the electrolytically produced disinfectants, which represent strong oxidants. A chemical reaction of the electrolytically generated disinfectants with the anode material is undesirable. It is therefore important that the material of the first anode region is resistant to oxidation. Since the first anode region consisting of an oxidation-stable material merely serves to disinfect the liquid to be treated, the surface and thus the cost thereof can be kept small.

In contrast to the prior art, a prevention of lime precipitation of the liquid to be treated in the region between the cathode and the at least partially made of a carbon material further anodic region takes place. Here, seed crystals form to stabilize lime dissolved in water. Since the limescale function of the water is mainly on the stabilization of the dissolved lime by means of these seed crystals, plays in the EP 0 175 123 B1 Descaling mechanism described by the lime deposit at the cathode only a minor role, ie, most of the dissolved in the liquid to be treated lime is stabilized by the seed crystals, whereby a lime deposit compared to the known device takes place at the cathode. Detachment of the lime from the cathode, for example by a polarity change on the electrolytic cell, is therefore less often necessary than in the prior art, whereby the service life of the electrodes is increased.

The isolated arrangement of the two anode regions, on the one hand it is possible to spatially separate the electrolytic treatment for disinfection and to prevent unwanted lime precipitation. On the other hand, the at least two mutually insulated anodes can be controlled separately. This is particularly advantageous because the disinfection and the prevention of unwanted Kalkausfällungen usually require different treatment times and intensities. Thus, the concentration of electrolytically generated free chlorine in the treated water must not exceed the limit value of 0.3 mg / l of the Drinking Water Ordinance, while the effectiveness of the electrolysis device for the prevention of stone formation after the DVGW worksheet W 512 must be at least 80%. In order to realize this, the anodes isolated from each other can be kept at different potentials, or else a potential can be applied to the mutually insulated anodes at different times with the aid of the electronic control device.

The device according to the invention therefore enables an efficient and cost-effective treatment of water or aqueous solutions against limescale deposits and at the same time a disinfection of the liquid to be treated. This is of great advantage, in particular in the hot water sector, because on the one hand, the tendency to form stones is particularly great due to the shift in the lime-carbonic acid balance and, on the other hand, many bacteria, such as legionella, can multiply particularly well in the hot water area.

In an advantageous embodiment of the invention, the carbon material of the further anode region contains activated carbon, graphite, carbon felt, graphite felt and / or a bed of carbon particles. Activated carbon is particularly suitable for this purpose due to its large surface area and also adsorbs any impurities present in the water. Graphite is characterized by its good conductivity. Finally, carbon and graphite felt have large surfaces, are easy to handle and easy to form. In addition, electrodes from a bed of carbon particles can assume almost any shape and be adapted to the given geometry. Due to their enormous surface they are characterized by a low resistance and thus by a high efficiency in the prevention of unwanted lime precipitation.

A further embodiment of the invention provides that at least one power supply projects into the carbon material.

Electrolysis devices with an anode region made of carbon or graphite felt, in which a power supply protrudes, have the effect proof after DVGW worksheet W 512, method for assessing the effectiveness of water treatment plants to reduce stone formation, achieved particularly good results.

The power supply is preferably made of an electrically conductive material, preferably of graphite, precious metal or coated with precious metal or mixed oxides titanium. Graphite electrodes are available inexpensively in many variants. The advantage of noble metal electrodes and electrodes made of titanium coated with noble metal or mixed oxides is their high resistance to oxidation.

In a particularly advantageous embodiment of the invention, the oxidation-stable material of the first anode region contains noble metal or titanium coated with noble metal or mixed oxides. These materials are particularly suitable in the anodic area, where a high chemical and electrochemical resistance is required. Titanium as a base metal may be formed in the form of a wire or as an expanded metal. It is easily malleable and can therefore easily be adapted to the given geometry.

For controlling the electrodes, an electronic control device may be provided.

In a further advantageous embodiment of the invention, a measuring cell for determining the content of free chlorine in the treated liquid is provided. This ensures that the limit value of the drinking water ordinance of 0.3 mg / l is not exceeded. At the same time it can be checked whether a minimum concentration of free chlorine is not exceeded in order to ensure a sufficient disinfection of the water to be treated. In addition, the measured value of the concentration of the free chlorine can be used to control the intensity of the electrolytic treatment.

Also particularly advantageous is an embodiment of the invention in which a metering device is provided for controlling the chloride content. As a result, for example, the chloride concentration in liquids with low be increased natural chloride content, so that even in these cases chlorine-containing disinfectants can be produced electrolytically in sufficient concentration.

Finally, an embodiment in which the cathode is brush-shaped, in particular with radially projecting bristles, is particularly preferred. Such a cathode is detailed in DE 198 52 956 C1 described.

Moreover, it is advantageous if means are provided for liberating the cathode from limescale during the operation of the device. Limescale deposits are caused by the increase in the pH in the cathode area and should be removed regularly to prevent blocking and isolation of the cathode surface. For this purpose, for example, serve a mechanical wiper, which brushes over the tips of the bristles of a brush-shaped cathode and thereby brings the deposited on the cathode surface lime crystals by a corresponding twisting or bending of the cathode to flake off. The cathode is thus easily freed automatically during operation of limescale. An otherwise necessary for cleaning the cathode otherwise polarity reversal of the electrodes is therefore superfluous.

It is particularly advantageous if the limescale protection function and disinfection of the liquid to be treated take place by means of an inventive method for the electrolytic treatment of water or aqueous solutions by means of an electrolysis device in which at least two electrodes of the electrolysis device are set to different electrical potentials, wherein the potential difference between the Electrodes are selected at least so large that electrolysis of the water and / or chloride ions contained in the water can take place, wherein the electrodes comprise at least one anode and one cathode. The electrolytic treatment of the water or the aqueous solutions takes place in two areas of the electrolysis device by means of two different anode regions, wherein a first anode region made of an oxidation-stable material and another anode region is at least partially made of a carbon material. The electrolytic treatment of the water or the aqueous solutions is carried out by means of at least two anodes electrically isolated from each other, wherein at least one of the electrically isolated anodes comprises the first anode region and at least one other of the electrically isolated anodes from the further anode region.

In a particularly preferred variant of the method according to the invention, the liquid to be treated first flows through the region of the electrolysis device in which the further anode region made of carbon material flows, and then through the region of the electrolysis device in which the first anode region made of oxidation-stable material is located , This avoids that electrolytically generated disinfections on the further anode part, which is made at least partially of carbon material, flow past, are adsorbed there or chemically abreact. This would significantly reduce their concentration and significantly weaken the effect of disinfection.

In a further variant of the method according to the invention, only a partial stream of the liquid to be treated flows through the region of the electrolysis device in which the first anode region made of oxidation-resistant material is located, this partial stream being mixed again into the main stream downstream of the electrolysis device. This avoids that the electrolytically produced disinfectants come into contact with the carbon material. In addition, the residence time of the throttled partial flow in the electrolytic disinfection device is sufficiently long, even at high total flow rates, to produce a sufficient amount of disinfectants.

The mutually insulated anodes can be controlled separately by means of an electronic control device and thereby kept at different electrical potentials.

In addition, it may be advantageous to feed the electrically isolated from each other anodes at different times with electricity.

In an advantageous variant of the method according to the invention, the concentration of free chlorine produced electrolytically from chloride ions in the treated liquid is measured.

A development of this variant provides that the intensity of the electrolytic treatment is controlled as a function of the measured values of the concentration of free chlorine.

In order to ensure a sufficient concentration of chloride ions in the solution to be treated, before the electrolytic treatment, chloride, preferably sodium chloride (common salt), can be added by means of a metering device in the flow direction.

In addition, it is advantageous if the cathode is freed during operation of limescale.

Further advantages of the invention will become apparent from the description and the drawings. Likewise, the features mentioned above and those listed further can be used individually or in any combination. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention.

Fig. 1

einen schematischen Vertikalschnitt einer nicht erfindungsgemäßen Vorrichtung; und

Fig. 2

einen schematischen Vertikalschnitt einer erfindungsgemäßen Vorrichtung mit zwei voneinander isolierten Anodenbereichen.

Show it:

Fig. 1

a schematic vertical section of a device not according to the invention; and

Fig. 2

a schematic vertical section of a device according to the invention with two mutually insulated anode regions.

Fig. 1 shows a section of a working on an electrolytic basis water treatment plant 1 with a housing 2, which has an inlet 3 for water to be treated and an outlet 4 for treated water. Inside the housing there is an electrolysis device with a brush-shaped cathode 5 and an anode, which comprises a power supply 6 and a graphite felt 7 . As a power supply 6 is for example a coated with noble metal mixed oxides titanium expanded metal or a platinum-plated titanium wire. The power supply 6 protrudes here only partially into the graphite felt 7, so that two different anode regions 8, 9 are formed. A first anode region 9 is not surrounded by the graphite felt 7, while another anode region 8 lies in the region of the graphite felt 7. To create a necessary for the electrolysis potential difference between the cathode 5 and the anode with the anode regions 8, 9 is a voltage source not shown in the figure with electronic control device.

The water to be treated first flows through the inlet 3 into the electrolysis device, which is located inside the housing 2. The water first flows through the brush-shaped cathode 5 and flows from there to the graphite felt 7. The taking place in the region between the cathode 5 and graphite felt 7 electrolysis of - water calcium carbonate seed crystals are formed, the lime in the adjustment of the lime-carbonic acid balance bind, so that calcification of subsequent installation facilities is largely prevented. The graphite felt 7 is fixed with diaphragms 10 , which simultaneously serve as spacers between the graphite felt 7 and the cathode 5. The water flows through a channel 11 to the anode region 9. Here is an electrolytic production of chlorine-containing disinfectants from chloride ions contained in the water instead. The water thus treated flows through the diaphragms 10 and flows via a channel 12 into the outlet 4. A water-impermeable partition wall 13 prevents the water from flowing directly from the area around the cathode 5 to the outlet 4 without flowing through the first anode area 9.

Fig. 2 shows a erfindungsgemäβe embodiment of a water treatment plant 1 ' with two mutually insulated anode regions 8', 9 '. The first anode region 9 'comprises only a wound platinum-plated titanium wire 14' and a power supply 15 '. In the further anode region 8 'protrudes, in contrast to the in Fig. 1 shown embodiment, a power supply line 6 ' completely in a graphite felt 7' into it.

The flow direction of the water in this embodiment corresponds to that in FIG Fig. 1 described flow direction. Here, too, the water first flows through the brush-shaped cathode 5 and flows from there to the graphite felt 7 ', wherein the calcium carbonate seed crystals contributing to the hardness stabilization are formed. At the first anode region 9 'around the platinum-plated titanium wire 14', which the water passes thereafter, the chlorine-containing disinfectants are generated electrolytically from chloride ions present in the water.

An advantage of this embodiment is that the two anodes are spatially separated and electrically isolated from each other, so that on the one hand formed disinfectant with the graphite felt 7 'does not come into contact and react with this and on the other hand separated both anodes with an electronic control device not shown in the figure can be controlled. This is particularly advantageous because the disinfection and the prevention of unwanted Kalkausfällungen usually require different treatment times and intensities. As an alternative to the graphite felt 7 ', for example, a bed of carbon particles is also conceivable.

Overall, there is a device or a method with which both a disinfection and a hardness stabilization of a liquid to be treated can be carried out inexpensively and efficiently.

LIST OF REFERENCE NUMBERS

1, 1 ' Water treatment plant 2 casing 3 Intake 4 outlet 5 cathode 6, 6 ' power supply 7, 7 ' graphite 8, 8 ' another anode area 9, 9 ' first anode area 10 diaphragm 11 channel 12 channel 13 partition wall 14 ' platinum-plated titanium wire 15 ' power supply

Claims (20)

1. Device for the electrolytic treatment of water or aqueous solutions, comprising an inlet (3) for the liquid to be treated, and an outlet (4) for the treated liquid, as well as an electrolysis unit comprising electrodes which are arranged between the inlet (3) and the outlet (4) and can be connected to mutually different electric potentials, wherein the potential difference is selected to be at least high enough that electrolysis of water and/or of chloride ions present in the water can be performed, wherein the electrodes comprise at least one anode and one cathode (5), and wherein a first anode area (9, 9'), which is produced from an oxidation-resistant material, and a further anode area (8, 8'), which is produced at least in part from a carbon material, are provided,
   characterized in that
   the first (9, 9') and the further anode area (8, 8') are arranged so that they are electrically insulated from each other.
2. Device according to claim 1, characterized in that the carbon material of the further anode area (8, 8') contains activated carbon, graphite, carbon felt, graphite felt (7, 7') and/or a bulk of carbon particles.
3. Device according to any one of the claims 1 or 2, characterized in that at least one current supply (6, 6') projects into the carbon material.
4. Device according to claim 3, characterized in that the current supply (6, 6'), is produced from an electrically conducting material, preferably from graphite, noble metal, or titanium that is coated with noble metal or with mixed oxides.
5. Device according to any one of the preceding claims, characterized in that the oxidation-resistant material of the first anode area (9, 9') contains noble metal or titanium that is coated with noble metal or with mixed oxides.
6. Device according to any one of the preceding claims, characterized in that an electronic control device is provided for controlling the electrodes.
7. Device according to any one of the preceding claims, characterized in that a measuring cell is provided for detecting the content of free chlorine in the treated liquid.
8. Device according to any one of the preceding claims, characterized in that a metering device is provided for controlling the chloride content.
9. Device according to any one of the preceding claims, characterized in that the cathode (5) has a brush-shaped design, in particular, having bristles which radially project in a star shape.
10. Device according to any one of the preceding claims, characterized in that means are provided for freeing the cathode (5) from lime deposits during operation of the device.
11. Method for electrolytic treatment of water or aqueous solutions using an electrolysis unit, in which at least two electrodes of the electrolysis device are connected to different electric potentials, wherein the potential difference between the electrodes is selected to be at least high enough that an electrolysis of water and/or of chloride ions present in the water can be performed, wherein the electrodes comprise at least one anode and one cathode (5), wherein the electrolytic treatment of the water or of the aqueous solutions is performed in two areas of the electrolysis unit by means of two different anode areas (8, 8', 9, 9'), wherein a first anode area (9, 9') is produced from an oxidation-resistant material and a further anode area (8, 8') is produced at least in part from a carbon material,
    characterized in that
    the electrolytic treatment of water or of the aqueous solutions is performed by means of at least two anodes that are electrically insulated from each other, wherein at least one of the electrically insulated anodes comprises the first anode area (9, 9') and at least one other of the electrically insulated anodes comprises the further anode area (8, 8').
12. Method according to claim 11, characterized in that the liquid to be treated initially flows through the area of the electrolysis unit, in which the further anode area (8, 8') produced form carbon material is located, and subsequently flows through the area of the electrolysis unit, in which the first anode area (9, 9') produced from oxidation-resistant material is located.
13. Method according to any one of the claims 11 or 12, characterized in that only a partial flow of the liquid to be treated flows through the area of the electrolysis unit, in which the first anode area (9, 9') produced from oxidation-resistant material is located, wherein this partial flow is added again to the main flow downstream of the electrolysis unit.
14. Method according to any one of the claims 11 through 13, characterized in that the electrically insulated anodes are controlled separately by means of an electronic control device.
15. Method according to claim 14, characterized in that the electrically insulated anodes are kept at different electric potentials.
16. Method according to claim 14 or 15, characterized in that the electrically insulated anodes are supplied with current at different times.
17. Method according to any one of the claims 11 through 16, characterized in that the concentration of the free chlorine, which was electrolytically produced from chloride ions, in the treated liquid is measured.
18. Method according to claim 17, characterized in that the intensity of the electrolytic treatment is controlled in dependence on the measured values of the concentration of free chlorine.
19. Method according to claim 17 or 18, characterized in that chloride, preferably sodium chloride (common salt), is added in the flow direction by means of a metering device prior to electrolytic treatment.
20. Method according to any one of the claims 11 through 19, characterized in that the cathode (5) is freed from lime deposits during operation.

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